In conventional plasma processing apparatuses, because plasma processing was conducted while controlling externally controllable RF power, RF frequency, gas pressure, gas flow rate, types of gas, and types of added gasses, it was impossible to control the energy and density of the ions which were directly injected into the substrate or the surfaces of the chamber. In order to obtain the optimal conditions for ion energy or density, a number of evaluations were conducted utilizing actual substrates, and based on the results thereof, the optimal conditions were determined empirically, so that this process required an enormous amount of labor. Furthermore, there were problems in that when high energy ions were injected into surface substrates during the plasma processing, damage was caused to the substrates, and when high energy ions were injected into the cheer surfaces, the cheer material was caused to sputter, and the substrate surfaces were contaminated with cheer material. It was essentially impossible to solve these problems while simultaneously determining the etching rate and etching form. For this reason, these problems presented a great obstacle to the realization of deep submicron ULSI having high performance and high reliability. In order to solve these problems, it is essential to precisely control the energy and density of the ions injected into the substrate surfaces, as well as the energy (plasma potential) of the ions injected into the chamber surfaces. Accordingly, there has been urgent demand for a method for measuring the energy and density of ions injected into a substrate during plasma excitation in a plasma processing apparatus, and for measuring the plasma potential, and additionally, for a method of controlling these.
An evaluation method employing a probe has been in common use as an accurate evaluation method for the energy and density of the ions in a plasma, and for the plasma potential; however, as a result of the sputtering of the probe material, there is a great possibility of the contamination of the substrate surfaces. Furthermore, an analysis method employing light absorption or light emission or lasers has been used as a method for the identification of the type of excitation in a plasma; however, as optical energy enters from the exterior, the plasma itself becomes disturbed. Furthermore, measurement of the energy or density distribution of the ions by means of mass spectrometry involves an electrode construction which is complicated, and some time is required for the analysis, so that such a method is unsuitable for real-time monitoring.
Furthermore, in previous apparatuses, only the externally controllable RF power, RF frequency, gas pressure, gas flow rate, type of gas, and type of added gas were controlled, so that it was essentially impossible to precisely control the energy or density of the ions or the plasma potential.
The present applicant has provided, in Japanese Patent Application No. Hei 2-252847, a technology capable of controlling the energy and density of the ions injected into a substrate body by means of the detection of the energy and density of ions injected into the substrate body. However, this technology centers only on the energy and density of the ions, and is not concerned with the control of other process parameters at desired values. That is to say, it was difficult to cause the energy and density of the ions to be reflected in process parameters in an easily applicable manner, and thus control these parameters, merely by means of the detection of the energy or density of the ions.
The present invention has as an object thereof to provide a plasma processing apparatus which is capable of precisely controlling the energy and density of ions injected into a substrate body, and which is capable of easily conducting the control of process parameters.